Mechanical couplings 10, as shown in FIG. 1, are used to couple pipes 12 and 14 to one another and effect a fluid tight joint. Couplings 10 may comprise a pair of segments 16 and 18 that are joined to one another end to end by fasteners 20 to circumferentially surround the ends of pipes 12 and 14. To effect a substantially rigid joint, i.e., a joint which resists relative rotation of the pipes 12 and 14 about their longitudinal axes, resists axial motion of the pipes relatively to one another due to internal pressure, and resist angular deflection of the pipes relatively to one another, it is advantageous to position circumferentially extending grooves 22 and 24 around each pipe. The grooves 22 and 24 are positioned in spaced relation to the ends of the pipes 12 and 14 and are sized to receive arcuately shaped keys 26 and 28 extending from each segment 16 and 18. Engagement of the keys 26 and 28 with grooves 22 and 24 substantially rigidizes the joint formed by coupling 10. Fluid tightness of the joint is ensured by a sealing member 30 positioned between the pipes 12 and 14 and the coupling segments 16 and 18.
Assembly of piping networks using mechanical pipe couplings 10 may entail that pipe stock be cut to a desired length, the cut pipe segments be reamed to remove burrs and sharp edges, and grooves such as 22 and 24 be formed in both ends of each cut pipe segment. The cut, reamed and grooved pipe segments may then be joined to one another using the couplings 10.
Forming circumferential grooves in pipes made of malleable materials such as plastics, copper, steel and aluminum is advantageously accomplished by cold working the material beyond its yield stress, thereby causing a permanent deformation in the material. Existing techniques for forming circumferential grooves in metal and plastic pipes entail sandwiching the pipe sidewall between the circumferences of two adjacent rotatable rollers. One roller, known as the back-up roller, is positioned on the inside of the pipe, and the other, known as the grooving roller, is positioned on the outside. The back-up roller has a concave die around its outer circumference and the grooving roller has a raised grooving surface around its outer circumference. With the pipe sidewall between them, the rollers are rotated in opposite directions and are forced toward one another so that they apply pressure to the sidewall. The die and the grooving surface traverse the pipe circumference and cooperate to cold work the sidewall and produce a circumferential groove of the desired size and shape. The rollers may move relatively to the pipe or the pipe may rotate about its longitudinal axis and move relatively to stationary rollers.
The method using a grooving roller and a back-up roller is effective at forming grooves in pipe walls while maintaining the roundness of the pipe because the pipe sidewall is mutually supported between the rollers and is never subjected to compressive point loads which would tend to collapse the pipe or force it out of round. Both rollers cooperate to work the material comprising the pipe, the grooving roller forming the groove and the back-up roller acting as a die to control the flow of material during cold working and precisely define the groove shape.
It is convenient, especially for larger diameter pipe stock and harder materials such as steel, to use electrically powered tools to perform the various operations. However, electrical power is not always available, especially at remote sites in the field. Therefore, it would be advantageous to have a pipe grooving tool that can be operated either using electrical power, when available, or manually, when electrical power is not available. Furthermore, it is less costly to have a single tool for both manual and power operation as opposed to having two separate tools, each dedicated to only one mode of operation.